Manufacture of lactic-acid esters



nown w. marnnson, or MONTREAL,

swrnrenn rA Ls, eunnnc, CANADA,

Lnrrrnn, or mon'rnnan, cnrmnn.

7 hers coin? a The Drawing.

This invention'relates to the manufacture of lactic acid esters and the object or the invention is the provision of a process by means of which the esters may be made easily, inexpensively and economically, in substantially anhydrous condition, in one operation directly from the corresponding alcohols without a separate preliminary preparation of lacticacid orits salts.

W riefiy, the process consists in causing the reaction ofacetaldehyde-cyanhydrin, an apomen 0H CHaCH +EtOH==OHaCH \COSH In carrying out the reaction, acetaldehydecyanhydrin may be firstprepared by the interaction of substantially anhydrous hydrocyanic acid and anhydrous acetaldehyde in presence of a trace of alkali or a cyanide. The cyanhydrin thus prepared is suitable for use without purification and may be admixed with water, in proportion of one to one molecule of water, and with a suitable amount of an alcohol and the correct pro portion of a mineral acid or a small excess to combine with the ammonia liberated. A slight excem of acid may be found advisable.

llhe mixture is then heated, when using ethyl alcohol,- to a temperature of about 80 C. for approximately three hours. A wide variation of temperature is possible for any alcohol and the range will vary depending on the alcohol used, but the heating should not be such'asiwill cause the temperature to rise to a point where the yield of the ester is seriously decreased, such as would ,occur at 160 0.

y suitable mineral acid may be used QUEBEC, AND KENNETH G. BL'AIKIE, 0F

molecule of cyanhydrin to approximately,

I -i 50,95 ar or c it;

ASSIGNOlR-S TO CANAID ELECTRO PROD- u nurecrunnor LAGTIC-AOID n srnns.

Application filed September 4,- i925. Serial-No. 54,552.

proximately equimolecular amount of water and an alcohol, n presence of a mineral acid sufiicient to combine wlth the ammonia liberated. The Water present is therefore less than would serve to hydrolyze all the cyanhydrin to lactic acid but it will be under stbod that the cyanhydrin goes directly to ester Without hydrolysis, The reactions theoretically take place ac cording to the following equations;-

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directly and in one stage from acetaldehydecyanhydrin and an alcohol bythe use of approximately only one molecule of water to each molecule of cyanhydrin, the reaction being theoretically corn:

but hydrochloric acid is found preferable, either dissolved in the reaction mixture or in the alcohol.

The following examples will serve to illustrate the carrying out of the process for the manufacture or ethyl lactate, but it will be understood that the invention is not limited to the production of this particular ester ,nor to the proportions, modes of operation,

temperatures, acid used, either for production of ethyl lactate or any other lactate, the same being purely illustrative.

Example I.

' ture and thetemperature maintained at about -3035 by means of cold Water. The container is Weighed from timeto time. When a total of 370 parts of hydrogen-chloride is product, which now is filled to a considerable present, the gas stream is cut off and the extent with a crystalline precipitate of ammonium chloride, is heated to approximately C. forthree hours, when-the reaction is over. After cooling, the solid ammonium chloride is filtered from the reaction product and thoroughly washed with a minimum uantity of alcohol. It will be noted from t e proportions used that only one molecule of water was added to one molecule of cyanhydrin and that the hydrogen-chloride is present in approximately 1% excess. The reaction product now consists of a mixture of unchan ed alcohol, which'is present in excess, an ethyl lactate, the cyanhydrin being converted almost quantitatively. The small trace of acid left in the reaction mixture is neutralized with a calculated amount of alcoholic ammonia and again filtered from a precipitated solid. The material can now be fractionated for the separation of the alcohol and the ethyl lactate by distillation,

either at ordinary pressure or in vacuo. A

small residue is left behind.

Example 11.

It may be found more convenient to add all the hydrogen-chloride in solution in alcohol, for which purpose a stock solution of this material may be kept. The following illustrates this method of carrying out the reaction 143.5 parts of acetaldehyde-cyanhydrin of 99% purity are admixed with 118 parts of ethyl alcohol and 26 parts of water, all b weight. This mixture is warmed to approximately 55 C. and 356.4 parts of alcoholic hydrogen-chloride are added, the concentration of hydrogen-chloride in the ethyl alcohol being 23.6%. The alcoholic hydrogen-chloride is run in slowly, the whole being vigorously stirred. The alcohol used is of such concentration as to make u the amount of water to two molecules or t irtysix parts. The reaction proceeds quiet-lg. The temperature should be kept below 70 by cooling if necessary. During the addition of the alcoholic hydrogen-chloride, ammonium chloride separates. After the addition of the solution, which takes about 2% hours, the reaction mixture is heated to 82- 85 C. for three hours. In carrying out the reaction, it appears necessary to keep the temperature below the boiling point of alcohol until most of the hydrogen-chloride has been taken up by the reaction, as otherwise the hydrogen-chloride and alcohol react to give ethyl chloride, with consequent loss of acid and alcohol.

When the reaction is complete, ammonium chloride is filtered off and washed with the minimum quantity of ethyl alcohol. The hydrogen chloride being present: excess,

the acidity is determined and the liquid neutralized with alcoholic potash, alcoholic ammonia, sodium acetate, or any other suitable neutralizing agent.

After filtering again from any precipitated solid, the product is distilled, preferably under diminished pressure, and finally fractionated at ordinary pressure, whereby the separation of alcohol and ethyl lactate is eflected.

The total ester recovered, with a boiling point of 148150 (1, equals 205.5 parts, being a yield of approximately the ammonium chloride recovered=l00 parts, being a yield of 93.6%; a small residue is left behind on fractionation, amounting to 7.5 parts.

In-the foregoing examples, ethyl alcohol has been used with production of ethyl lactate. In a manner similar to that of either of the examples methyl lactate may be made and, keeping the correct molecular proportions, similar results are obtained as regards yield. Proceeding in similar manner and using other alcohols, either aliphatic or aromatic, the corresponding esters of lactic acid mav be roduced.

onsi erable variation may be made in the method, both in proportions and in tem erature, without departing from the spirit of the invention. While the reaction will proceed at room temperature, the rate of reaction is not economical and heating is preferable and may be carried to any temperature up to the point already noted.

Having thus described our invention, what y we claim is 1. A process for the production of lactic acid esters, which comprises reacting together acetaldehyde-cyanhydrin and an alcohol in presence of a mineral acid and less water than would serve to hydrolyze all the cyanhydrin to lactic acid.

2. A process for the production of lactic acid esters, which comprises reacting together acetaldehyde-cyanhydrin and an alcohol in presence of a mineral acid and water in amount substantially equimolecular with the cyanhydrin.

3. A process for the production of lactic acid esters, which comprises reacting together acetaldehyde-cyanhydrin and an alcohol in presence of a mineral acid in slight excess and Water in amount less than would serve to hydrolyze all the cyanhydrin to lactic acid.

4. A process for the production of lactic acid esters, which comprises reacting together acetaldehyde-cyanhydrin and an alcohol in presence of a mineral acid in slight excess and water in amount substantially equimolecular with the cyanhydrin.

5. A process for the production of lactic acid esters, which comprises reacting together acetaldehyde-cyanhydrin and an alcohol in presence of a mineral acid and less Water than would serve to hydrolyze all the .Which the mineral formed ester.

cyanhydrinto lactic acid, and heating the mixture at at ten'iperature below that at acid reacts -\Vitl1 the 6. A process for the production of lacti acid esters, which comprises reacting together acet aldehydc cyanhydrin and an alcohol in presence of a mineral acid and Water in amount substantially equimolecular With the cyanhydrin, and heating the mix-- acid esters,' which comprises" reacting together 'acetaldehyde-cyanhydrinand analcohol in presence of a mineral j acidf in amount suflicient tocombinewith the libel:

ated ammonia and inpresence of less water than would serve to hydrolyze all-the cyan'- hydrin to lactic acid. a p

8. Aprocess forthe production of lactic acid esters, which comprises reacting together acetaldehyde-.cyanhydrin and an alv lactate, which comprisesrea'ctingi together acetaldehyde-cyanhydrin and ethyl alcohol cohol in presence-- of a mineral acid in amount suflicient to combine with the lib-- erated ammonia and in presence of Water in amount substantially 'equimolecular; with the.

cyanhydrin.

9. A' processjfor the production of ethyl lactate, which comprises reacting together acetaldehyde-cya'nhydrin 1 and ethyl alcohol" I in presence of a mineral acid and less water v than would serve to hydrolyze all the cyanhydrin to lactic-acid.-

the production of new;

1 10. A process for the production of ethyllactate, which comprises reacting together. acetaldehyde-cyanhydrin and ethyl alcohol in presence'o'f hydrochloric-acid and less 7 .water than would serve to hydrolyze'all the cyan'nydrin to lactic acid; "11. A processfor the production of ethyl lactate, which comprises reacting together acetaldeh-yde cy'anhydrin and ethyl alcohol in; presence .of a mineral acid and Water in amount substantially equimolecular with v the cyanhydrin.

12.. A process for the production of ethyl lactate, ,which :comprises reacting together acetaldehyde-cyanhydrin and ethyl alcohol in presence of hydrochloric acid andj'wat'er in amount substantially equimolecular "with.

the cyanhydrini .13. A process lactate, which comprises reacting together acetaldehyde=cyanhydrin "and ethyl alcohol 'in presence of sufficient hydrochloric acidto combine with 'theliberated ammoniaand in for the production of ethylpresence of less Water than would. serve to hydrolyze all the cyanhydrin to lactic'acid, Y

14; A processfor the production of ethyl in presence of sulficient hydrochloric acid, to

presence of Water in amount substantially equimolecular' with the .cyanhydrin.

In Witness whereof, we have hereunto set our hands.

' KENNETH c. BLAIKIE,

. HOWARD W. MATHEsoN. 

